1
Q
What is the main focus of biochemistry?
A. Study of living organisms’ chemical processes
B. Study of planets
C. Study of tissues under microscope
D. Study of fossils
A
A
2
Q
Which four aspects does biochemistry mainly study?
A. Energy, light, heat, sound
B. Structure, function, metabolism, regulation
C. Growth, reproduction, decay, death
D. Movement, respiration, reproduction, excretion
A
B
3
Q
The central dogma of molecular biology describes the flow of genetic information as:
A. Protein → RNA → DNA
B. DNA → RNA → Protein
C. RNA → Protein → DNA
D. RNA → DNA → Protein
A
B
4
Q
The main energy currency of the cell is:
A. NADH
B. ATP
C. Glucose
D. GTP
A
B
5
Q
Diabetes mellitus is caused by:
A. Lipid metabolism defect
B. Glucose metabolism imbalance
C. Nucleic acid defect
D. Protein mutation
A
B
6
Q
Which disease is caused by substitution of Glu → Val in hemoglobin?
A. Cystic fibrosis
B. Sickle cell disease
C. Thalassemia
D. Hemophilia
A
B
7
Q
Which law governs energy in living systems?
A. Law of Segregation
B. Law of Thermodynamics
C. Law of Independent Assortment
D. Law of Motion
A
B
8
Q
What are the four major biomolecules?
A. Proteins, carbohydrates, lipids, nucleic acids
B. Proteins, water, enzymes, vitamins
C. Nucleic acids, ions, hormones, ATP
D. Lipids, enzymes, carbohydrates, vitamins
A
A
9
Q
Macromolecules are polymers made from:
A. Sugars
B. Monomeric units
C. Gases
D. Vitamins
A
B
10
Q
A change in protein folding affects which level of structure?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
A
C
11
Q
The main structural component of biological membranes is:
A. Proteins
B. Phospholipids
C. Cholesterol
D. Carbohydrates
A
B
12
Q
Which model best describes the membrane?
A. Solid-state model
B. Fluid mosaic model
C. Rigid bilayer model
D. Static sheet model
A
B
13
Q
Cholesterol in membranes primarily:
A. Provides energy
B. Stabilizes and modulates fluidity
C. Forms ion channels
D. Acts as enzyme
A
B
14
Q
Integral proteins are:
A. Found only on the membrane surface
B. Completely embedded or spanning the bilayer
C. Free-floating in cytoplasm
D. Bound only to carbohydrates
A
B
15
Q
Peripheral proteins are:
A. Hydrophobic proteins spanning the membrane
B. Surface-associated, not embedded
C. DNA-binding proteins
D. Found in nucleus
A
B
16
Q
The carbohydrate portions of membranes function in:
A. Cell recognition and signaling
B. Energy storage
C. Protein synthesis
D. Osmotic regulation
A
A
17
Q
Simple diffusion moves molecules:
A. Against concentration gradient
B. Along concentration gradient without energy
C. Using ATP
D. Using protein carriers
A
B
18
Q
Which process requires ATP?
A. Osmosis
B. Facilitated diffusion
C. Active transport
D. Simple diffusion
A
C
19
Q
The Na⁺/K⁺ ATPase pump moves:
A. 2 Na⁺ in, 3 K⁺ out
B. 3 Na⁺ out, 2 K⁺ in
C. 3 Na⁺ in, 2 K⁺ out
D. Equal Na⁺ and K⁺
A
B
20
Q
Cystic fibrosis is due to mutation in:
A. GLUT transporter
B. CFTR chloride channel
C. Na⁺/K⁺ ATPase
D. Aquaporin
A
B
21
Q
Familial hypercholesterolemia is caused by:
A. Defective LDL receptor
B. Lack of insulin
C. Overproduction of HDL
D. Absence of phospholipids
A
A
22
Q
Monosaccharides include:
A. Sucrose, maltose, lactose
B. Glucose, fructose, galactose
C. Cellulose, glycogen, starch
D. Glycerol, acetone, ethanol
A
B
23
Q
The chemical formula of a hexose monosaccharide is:
A. C₆H₁₂O₆
B. C₅H₁₀O₅
C. C₄H₈O₄
D. C₇H₁₄O₇
A
A
24
Q
The bond connecting monosaccharides is a:
A. Peptide bond
B. Glycosidic bond
C. Phosphodiester bond
D. Hydrogen bond
A
B
25
The storage polysaccharide in animals is:
A. Cellulose
B. Glycogen
C. Amylose
D. Amylopectin
B
26
The enzyme lacking in lactose intolerance is:
A. Maltase
B. Lactase
C. Sucrase
D. Amylase
B
27
Cellulose differs from starch because:
A. It contains β-1,4 linkages
B. It is branched
C. It stores energy
D. It is a protein
A
28
Glycogen contains which type of linkages?
A. α-1,4 and α-1,6
B. β-1,4 and β-1,6
C. α-1,2 and β-1,3
D. α-1,5 only
A
29
Glycosaminoglycans (GAGs) are:
A. Branched oligosaccharides
B. Long unbranched polysaccharides
C. Proteins with sugar groups
D. Fats with carbohydrates
B
30
The repeating units in GAGs usually include:
A. Amino sugars and uronic acid
B. Peptides and alcohols
C. Fatty acids and cholesterol
D. Purines and pyrimidines
A
31
Which GAG is not sulfated and found in synovial fluid?
A. Heparin
B. Hyaluronic acid
C. Chondroitin sulfate
D. Keratan sulfate
B
32
Hurler syndrome is due to deficiency of:
A. Iduronate sulfatase
B. α-L-iduronidase
C. Glucocerebrosidase
D. Hexosaminidase A
B
33
Tay–Sachs disease involves accumulation of:
A. GM₂ ganglioside
B. Heparin
C. Glycogen
D. Uric acid
A
34
The enzyme deficient in Tay–Sachs is:
A. β-glucosidase
B. Hexosaminidase A
C. Sphingomyelinase
D. Glucocerebrosidase
B
35
Gaucher disease involves deficiency of:
A. Hexosaminidase A
B. Glucocerebrosidase
C. Iduronidase
D. Lactase
B
36
Digoxin inhibits:
A. Na⁺/K⁺ ATPase
B. GLUT transporter
C. ATP synthase
D. Ca²⁺ pump
A
37
Glycoproteins are important for:
A. Cell–cell recognition and immunity
B. Energy storage
C. Nerve conduction only
D. Lipid transport
A
38
The bond joining amino acids is a:
A. Peptide bond
B. Hydrogen bond
C. Glycosidic bond
D. Ionic bond
A
39
Which level of protein structure involves α-helices and β-sheets?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
B
40
Which level involves multiple polypeptide subunits?
A. Primary
B. Tertiary
C. Quaternary
D. Secondary
C
41
Denaturation destroys which structures?
A. Only primary
B. Secondary, tertiary, quaternary
C. All levels including primary
D. Only quaternary
B
42
Enzymes speed up reactions by:
A. Increasing activation energy
B. Lowering activation energy
C. Consuming substrates
D. Changing reaction equilibrium
B
43
A molecule with both positive and negative charges at physiological pH is a:
A. Ion
B. Zwitterion
C. Radical
D. Buffer
B
44
Phenylketonuria is due to deficiency of:
A. Phenylalanine hydroxylase
B. Tyrosinase
C. Lactase
D. Transaminase
A
45
The mnemonic “PVT TIM HALL” helps remember:
A. Nonpolar amino acids
B. Essential amino acids
C. Basic amino acids
D. Aromatic amino acids
B
46
The essential amino acids are:
PVT TIM HALL → Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine, Leucine, Lysine
47
Hemoglobin has how many subunits?
A. 2
B. 3
C. 4
D. 6
C 4 (2α + 2β)
48
The prosthetic group in hemoglobin is:
A. Heme (Fe²⁺)
B. Myoglobin
C. FAD
D. NAD⁺
A
49
The Bohr effect states that increased CO₂ or decreased pH leads to:
A. Increased O₂ affinity
B. Decreased O₂ affinity
B
50
Fetal hemoglobin (HbF) has:
A. Lower O₂ affinity
B. Higher O₂ affinity
B
51
Which of the following is a fibrous protein?
A. Hemoglobin
B. Myoglobin
C. Collagen
D. Albumin
C
52
Which of the following is a globular protein?
A. Keratin
B. Collagen
C. Actin
D. Hemoglobin
D
53
Which type of protein provides structural support and is generally insoluble?
A. Globular proteins
B. Fibrous proteins
C. Enzymes
D. Membrane proteins
B
54
Which amino acid is found at every third position in collagen?
A. Glycine
B. Proline
C. Alanine
D. Lysine
A
55
Vitamin C is required for which post-translational modification in collagen synthesis?
A. Hydroxylation of proline and lysine
B. Carboxylation of glutamate
C. Methylation of histidine
D. Phosphorylation of serine
A
56
Scurvy is caused by deficiency of:
A. Vitamin A
B. Vitamin B6
C. Vitamin C
D. Vitamin D
C
57
Osteogenesis imperfecta is caused by mutation in:
A. Elastin gene
B. Collagen type I gene
C. Keratin gene
D. Actin gene
B
58
Ehlers–Danlos syndrome is due to:
A. Vitamin C deficiency
B. Collagen synthesis defect
C. Iron deficiency
D. Lack of elastin
B
59
Fibrous proteins are generally:
A. Soluble and spherical
B. Insoluble and elongated
C. Hydrophilic and globular
D. Amphipathic
B
60
Globular proteins such as enzymes are primarily:
A. Structural
B. Catalytic and soluble
C. Insoluble and fibrous
D. Inactive in solution
B
61
Which of the following is a lipid?
A. Glycogen
B. Triglyceride
C. Protein
D. Cellulose
B
62
The basic unit of triglycerides consists of:
A. Glycerol and three fatty acids
B. Three amino acids
C. Two sugars
D. One nucleotide
A
63
Which of the following lipids is the main component of biological membranes?
A. Triglycerides
B. Phospholipids
C. Cholesterol esters
D. Waxes
B
64
Cholesterol serves as a precursor for:
A. RNA
B. Steroid hormones and bile acids
C. Amino acids
D. Polysaccharides
B
65
Which lipid contributes most to membrane fluidity?
A. Cholesterol
B. Triglyceride
C. Phosphatidylcholine
D. Sphingomyelin
A
66
The main storage form of energy in humans is:
A. Glycogen
B. ATP
C. Triglycerides
D. Glucose
C
67
HDL is considered “good cholesterol” because:
A. It delivers cholesterol to tissues
B. It removes cholesterol from tissues to the liver
C. It blocks cholesterol synthesis
D. It increases LDL levels
B
68
LDL is considered “bad cholesterol” because:
A. It promotes lipid degradation
B. It transports cholesterol to tissues, leading to plaque buildup
C. It removes cholesterol from tissues
D. It lowers blood triglycerides
B
69
Atherosclerosis is primarily caused by:
A. High HDL levels
B. High LDL levels
C. Low triglycerides
D. High glucose
B
70
Niemann–Pick disease results from deficiency of:
A. Hexosaminidase A
B. Sphingomyelinase
C. Glucocerebrosidase
D. α-L-iduronidase
B
71
Gaucher disease results from deficiency of:
A. Glucocerebrosidase
B. Hexosaminidase B
C. Sphingomyelinase
D. Lactase
A
72
Which of the following is NOT a function of lipids?
A. Energy storage
B. Membrane structure
C. Enzyme catalysis
D. Hormone synthesis
C
73
Which lipid forms the myelin sheath?
A. Sphingolipid
B. Triglyceride
C. Phospholipid
D. Waxes
A
74
Lipoproteins transport lipids through:
A. Digestive tract
B. Blood plasma
C. Urine
D. Lymph nodes only
B
75
Which of the following is NOT a function of lipids?
A. Energy storage
B. Membrane structure
C. Enzyme catalysis
D. Hormone synthesis
C
76
Which of the following statements about phospholipids is TRUE?
A. They are hydrophobic only.
B. They contain a polar head and two nonpolar tails.
C. They store energy in adipose tissue.
D. They form rigid barriers
B
77
The phospholipid bilayer is described as:
A. Fluid mosaic
B. Static bilayer
C. Crystalline solid
D. Protein sheet
A
78
Which of the following fatty acids is essential?
A. Palmitic acid
B. Oleic acid
C. Linoleic acid
D. Stearic acid
C
79
Which of the following lipoproteins carries dietary lipids from the intestine?
A. HDL
B. LDL
C. VLDL
D. Chylomicrons
D
80
The lipid soluble in water the least is:
A. Cholesterol
B. Fatty acid
C. Triglyceride
D. Phospholipid
C
81
Which enzyme is defective in carnitine deficiency?
A. Carnitine acyltransferase
B. Lipase
C. Glucose oxidase
D. Catalase
A
82
What is the general structure of an amino acid?
A. Central carbon, H, amino group, carboxyl group, and R group
B. Two carboxyl groups and a phosphate
C. Only R group and hydrogen
D. Three hydroxyl groups
A
83
Which amino acid is symbolized by Ala (A)?
A. Alanine
B. Arginine
C. Aspartic acid
D. Asparagine
A
84
Which amino acid has the 3-letter code “Gly” and 1-letter code “G”?
A. Glycine
B. Glutamine
C. Glutamic acid
D. Glycolic acid
A
85
The amino acid “Val” has the 1-letter code:
A. V
B. L
C. A
D. F
A
86
The 3-letter code “Leu” and 1-letter “L” represent:
A. Lysine
B. Leucine
C. Levorine
D. Lactic acid
B
87
The amino acid “Ile (I)” is:
A. Isoleucine
B. Imidazole
C. Inosine
D. Indole
A
88
The sulfur-containing amino acid “Met (M)” is:
A. Methionine
B. Methylamine
C. Malate
D. Mucine
A
89
The cyclic amino acid with 3-letter “Pro” and 1-letter “P” is:
A. Phenylalanine
B. Proline
C. Pyruvate
D. Phosphate
B
90
Which aromatic amino acid has the code Phe (F)?
A. Phenylalanine
B. Proline
C. Phosphate
D. Phenytoin
A
91
Which amino acid has a hydroxyl group and the code Ser (S)?
A. Serine
B. Sucrose
C. Selenocysteine
D. Silicate
A
92
The 3-letter code Thr (T) represents:
A. Threonine
B. Tyrosine
C. Thiamine
D. Thrombin
A
93
The amino acid Tyr (Y) is:
A. Tyrosine
B. Tryptophan
C. Threonine
D. Thiamine
A
94
The aromatic amino acid with 3-letter “Trp” and 1-letter “W” is:
A. Tryptophan
B. Tyrosine
C. Threonine
D. Thymine
A
95
The polar amino acid Asn (N) stands for:
A. Asparagine
B. Aspartic acid
C. Alanine
D. Arginine
A
96
The acidic amino acid with 3-letter “Asp” and 1-letter “D” is:
A. Aspartic acid
B. Asparagine
C. Adenine
D. Alanine
A
97
The acidic amino acid “Glu (E)” stands for:
A. Glutamic acid
B. Glutamine
C. Glycerol
D. Glucose
A
98
The amino acid “Gln (Q)” refers to:
A. Glutamine
B. Glutamic acid
C. Glycine
D. Glucose
A
99
The basic amino acid “Lys (K)” is:
A. Lysine
B. Leucine
C. Lactic acid
D. Lipase
A
100
The basic amino acid with guanidino group “Arg (R)” is:
A. Arginine
B. Aspartate
C. Alanine
D. Adenine
A
101
The imidazole-containing amino acid “His (H)” is:
A. Histidine
B. Homocysteine
C. Hydroxyproline
D. Hexose
A
102
Which amino acid has the smallest side chain (H)?
Glycine
103
Which amino acid introduces a kink in protein chains due to its cyclic structure?
Proline
104
Which amino acid contains a thiol (-SH) group?
Cysteine
105
Two cysteine residues can form:
Disulfide bonds
106
Which amino acids are aromatic?
Phenylalanine, Tyrosine, Tryptophan
107
Which amino acids are acidic?
Aspartic acid, Glutamic acid
108
Which amino acids are basic?
Lysine, Arginine, Histidine
109
Nonpolar amino acids include:
Gly, Ala, Val, Leu, Ile, Met, Pro, Phe, Trp
110
Polar uncharged amino acids include:
Ser, Thr, Cys, Asn, Gln, Tyr
111
Amino acids that are essential for humans include:
PVT TIM HALL
112
Enzymes are primarily composed of:
A. Lipids
B. Proteins
C. Carbohydrates
D. Nucleic acids
B
113
The function of enzymes is to:
A. Increase activation energy
B. Lower activation energy
C. Change the equilibrium constant
D. Provide energy to reactions
B
114
The region of an enzyme where substrate binds is called the:
A. Regulatory site
B. Allosteric site
C. Active site
D. Binding pocket
C
115
Which type of enzyme catalyzes oxidation–reduction reactions?
A. Transferase
B. Hydrolase
C. Oxidoreductase
D. Lyase
C
116
Which class of enzyme transfers functional groups from one molecule to another?
A. Oxidoreductase
B. Transferase
C. Hydrolase
D. Ligase
B
117
Which enzyme catalyzes bond formation using ATP?
A. Lyase
B. Ligase
C. Transferase
D. Isomerase
B
118
Which of the following enzymes catalyzes hydrolysis reactions?
A. Hydrolase
B. Transferase
C. Lyase
D. Oxidoreductase
A
119
The enzyme that rearranges functional groups within a molecule is a:
A. Isomerase
B. Hydrolase
C. Ligase
D. Oxidoreductase
A
120
Coenzymes are best described as:
A. Protein components of enzymes
B. Nonprotein organic molecules assisting enzymes
C. Metal ions serving as enzyme inhibitors
D. Products of enzyme catalysis
B
121
A cofactor that is a metal ion example is:
A. NAD⁺
B. FAD
C. Zn²⁺
D. CoA
C
122
A coenzyme derived from niacin is:
A. NAD⁺
B. FAD
C. CoA
D. TPP
A
123
A coenzyme derived from riboflavin (vitamin B₂) is:
A. NAD⁺
B. FAD
C. Biotin
D. CoA
B
124
The coenzyme responsible for acyl group transfer is:
A. Coenzyme A (CoA)
B. FAD
C. NAD⁺
D. Thiamine pyrophosphate
A
125
The Michaelis–Menten constant (Km) represents:
A. The maximum rate of reaction
B. The substrate concentration at half Vmax
C. The enzyme concentration
D. The inhibitor concentration
B
126
A lower Km value indicates:
A. Low substrate affinity
B. High substrate affinity
C. Enzyme denaturation
D. Low catalytic efficiency
B
127
Vmax represents:
A. The substrate concentration at half binding
B. The maximum rate of an enzyme reaction
C. The point where enzyme stops functioning
D. The lowest reaction rate
B
128
Which of the following best describes a competitive inhibitor?
A. Binds to active site, competes with substrate
B. Binds to allosteric site only
C. Irreversibly destroys the enzy
A
129
Competitive inhibition can be overcome by:
A. Increasing substrate concentration
B. Increasing inhibitor concentration
C. Lowering enzyme concentration
D. Decreasing temperature
A
130
Noncompetitive inhibition differs because:
A. Inhibitor binds to allosteric site
B. Km decreases and Vmax unchanged
C. Inhibitor resembles the substrate
D. It is reversible only
A
131
In noncompetitive inhibition, Vmax is:
A. Increased
B. Decreased
C. Unchanged
D. Infinite
B
132
Allosteric enzymes are regulated by:
A. Substrate concentration only
B. Binding of activators or inhibitors at non-active sites
C. DNA methylation
D. pH changes only
B
133
Feedback inhibition is a type of:
A. Competitive inhibition
B. Noncompetitive inhibition
C. Product inhibition
D. Irreversible inhibition
B
134
Enzyme denaturation affects which structures?
A. Secondary and tertiary
B. Primary only
C. Primary and quaternary
D. None
A
135
Optimum temperature for most human enzymes is around:
A. 25°C
B. 37°C
C. 50°C
D. 70°C
B
136
Which enzyme converts starch to maltose?
A. Amylase
B. Maltase
C. Sucrase
D. Lactase
A
137
Which enzyme deficiency causes phenylketonuria (PKU)?
A. Tyrosinase
B. Phenylalanine hydroxylase
C. Glucose oxidase
D. Transaminase
B
138
Maple Syrup Urine Disease results from deficiency of:
A. Branched-chain α-ketoacid dehydrogenase
B. Phenylalanine hydroxylase
C. Tyrosine aminotransferase
D. Glucose-6-phosphatase
A
139
The enzyme deficiency in G6PD deficiency affects which pathway?
A. Glycolysis
B. Pentose phosphate pathway
C. Citric acid cycle
D. Urea cycle
B
140
G6PD deficiency leads to:
A. Hemolysis due to oxidative stress
B. Hypoglycemia
C. Dehydration
D. Lactic acidosis
A
141
Which enzyme is inhibited by cyanide?
A. Cytochrome oxidase
B. Amylase
C. Hexokinase
D. Lactate dehydrogenase
A
142
Which coenzyme is required by transaminases?
A. Pyridoxal phosphate (Vitamin B6)
B. Biotin
C. FAD
D. NAD⁺
A
143
Which coenzyme is used in carboxylation reactions?
A. Biotin
B. FAD
C. NAD⁺
D. CoA
A
144
Thiamine pyrophosphate (TPP) is a coenzyme for:
A. Decarboxylation reactions
B. Dehydrogenation reactions
C. Hydrolysis reactions
D. Transamination reactions
A
145
Which coenzyme is used in carboxylation reactions?
A. Biotin
B. FAD
C. NAD⁺
D. CoA
A
146
Enzyme kinetics graphs (Michaelis–Menten plots) have which shape?
A. Linear
B. Hyperbolic
C. Sigmoidal
D. Parabolic
B
147
Allosteric enzyme kinetics graphs are:
A. Hyperbolic
B. Linear
C. Sigmoidal
D. Exponential
C
148
Which of the following statements about enzyme catalysts is TRUE?
A. They alter equilibrium
B. They increase reaction rate
C. They get consumed in reactions
D. They are non-specific
B
149
Isoenzymes are:
A. Chemically identical enzymes with different functions
B. Different forms of an enzyme catalyzing the same reaction
C. Mutated inactive enzymes
D. Nonprotein cofactors
B
150
Which enzyme’s isoenzymes are used in diagnosing myocardial infarction?
A. Amylase
B. Lactate dehydrogenase (LDH)
C. Catalase
D. Sucrase
B
151
Enzyme activity is measured by:
A. The number of molecules synthesized
B. Rate of substrate conversion per unit time
C. Enzyme concentration
D. Amount of cofactor present
B
152
An irreversible enzyme inhibitor:
A. Binds temporarily to the enzyme
B. Forms a covalent bond, permanently inactivating the enzyme
C. Can be reversed by increasing substrate
D. Lowers Km
B
153
Metabolism refers to:
A. All chemical reactions occurring in a cell
B. Only catabolic reactions
C. Only anabolic reactions
D. Energy storage only
A
154
Anabolism is:
A. Breakdown of molecules to release energy
B. Synthesis of complex molecules from simpler ones
C. Conversion of ATP to ADP
D. Oxidation of nutrients
B
155
Catabolism is:
A. Energy-requiring biosynthesis
B. Energy-releasing breakdown of molecules
C. Formation of peptide bonds
D. DNA replication
B
156
The main energy currency of the cell is:
A. GTP
B. ATP
C. NADH
D. AMP
B
157
The high-energy bonds in ATP are located between:
A. Adenine and ribose
B. Ribose and phosphate
C. Phosphate groups
D. Carbon and nitrogen
C
158
Hydrolysis of ATP to ADP + Pi releases approximately:
A. 1 kcal/mol
B. 7.3 kcal/mol
C. 20 kcal/mol
D. 50 kcal/mol
B
159
Which process occurs in the cytoplasm and does not require oxygen?
A. Electron transport chain
B. Glycolysis
C. Krebs cycle
D. Oxidative phosphorylation
B
160
The first enzyme of glycolysis is:
A. Phosphofructokinase-1
B. Hexokinase
C. Pyruvate kinase
D. Glucose-6-phosphatase
B
161
The rate-limiting enzyme of glycolysis is:
A. Hexokinase
B. Phosphofructokinase-1 (PFK-1)
C. Enolase
D. Pyruvate dehydrogenase
B
162
The final product of aerobic glycolysis is:
A. Lactate
B. Ethanol
C. Pyruvate
D. Acetyl-CoA
C
163
Anaerobic conversion of pyruvate produces:
A. Lactate
B. Acetyl-CoA
C. Glucose
D. Citrate
A
164
Which enzyme links glycolysis to the Krebs cycle?
A. Lactate dehydrogenase
B. Pyruvate dehydrogenase complex
C. Glucose-6-phosphatase
D. Malate dehydrogenase
B
165
The citric acid cycle occurs in the:
A. Cytoplasm
B. Mitochondrial matrix
C. Nucleus
D. Endoplasmic reticulum
B
166
Each turn of the Krebs cycle yields how many NADH molecules?
A. 1
B. 2
C. 3
D. 4
C
167
Which Krebs cycle intermediate condenses with acetyl-CoA to form citrate?
A. Malate
B. Oxaloacetate
C. Succinate
D. Fumarate
B
168
During the electron transport chain, oxygen serves as:
A. Electron donor
B. Final electron acceptor
C. ATP synthase substrate
D. Proton pump
B
169
How many ATP are produced from complete aerobic oxidation of one glucose molecule?
A. 2
B. 12
C. 30–32
D. 100
C
170
Which complex of the electron transport chain is inhibited by cyanide?
A. Complex I
B. Complex II
C. Complex III
D. Complex IV (cytochrome oxidase)
D
171
ATP synthase is found in the:
A. Cytosol
B. Inner mitochondrial membrane
C. Outer mitochondrial membrane
D. Nucleus
B
172
Which of the following is an uncoupler of oxidative phosphorylation?
A. Rotenone
B. Oligomycin
C. 2,4-Dinitrophenol (DNP)
D. Antimycin A
C
173
Glycogen is primarily stored in:
A. Brain and lung
B. Liver and muscle
C. Kidney and skin
D. Heart and pancreas
B
174
The enzyme that adds glucose units to glycogen is:
A. Glycogen phosphorylase
B. Glycogen synthase
C. Glucokinase
D. Glucose-6-phosphatase
B
175
Which enzyme releases glucose from glycogen during fasting?
A. Glycogen synthase
B. Glycogen phosphorylase
C. Hexokinase
D. Phosphofructokinase
B
176
Insulin stimulates:
A. Glycogenesis
B. Glycogenolysis
C. Gluconeogenesis
D. Lipolysis
A
177
Glucagon stimulates:
A. Glycolysis
B. Glycogenolysis and gluconeogenesis
C. Protein synthesis
D. Fat storage
B
178
The Cori cycle links:
A. Liver and brain
B. Muscle and liver
C. Kidney and heart
D. Intestine and pancreas
B
179
The Cori cycle involves conversion of:
A. Lactate → Glucose in liver
B. Glucose → Lactate in liver
C. Pyruvate → Alanine
D. Fats → Ketones
A
180
β-oxidation of fatty acids occurs in:
A. Cytoplasm
B. Mitochondrial matrix
C. Nucleus
D. Peroxisome only
B
181
The first step in β-oxidation requires:
A. Carnitine transport into mitochondria
B. ATP synthase
C. Citrate synthase
D. Glucose oxidase
A
182
Ketone bodies are produced from:
A. Acetyl-CoA
B. Glucose
C. Fatty acids only
D. Amino acids
A
183
During prolonged fasting, the brain uses mainly:
A. Glucose
B. Amino acids
C. Ketone bodies
D. Fatty acids
C
184
Gluconeogenesis occurs mainly in the:
A. Liver and kidney
B. Muscle only
C. Adipose tissue
D. Brain
A
185
Which enzyme bypasses pyruvate kinase in gluconeogenesis?
A. Pyruvate carboxylase and PEP carboxykinase
B. Hexokinase
C. Glucokinase
D. Enolase
A
186
Which vitamin serves as a cofactor for carboxylation reactions in gluconeogenesis?
A. Biotin
B. Thiamine
C. Riboflavin
D. Niacin
A
187
Which process directly produces the most ATP?
A. Glycolysis
B. Krebs cycle
C. Electron transport chain and oxidative phosphorylation
D. β-oxidation
C
188
In mitochondria, protons are pumped into the:
A. Matrix
B. Intermembrane space
C. Outer membrane
D. Cytosol
B
189
Which compound acts as a common intermediate for carbohydrate, fat, and protein metabolism?
A. Acetyl-CoA
B. Pyruvate
C. Lactate
D. Oxaloacetate
A
190
Which pathway provides ribose and NADPH for biosynthesis?
A. Glycolysis
B. Pentose phosphate pathway
C. Citric acid cycle
D. β-oxidation
B
191
NADPH is primarily used for:
A. ATP production
B. Biosynthetic reductions and antioxidant defense
C. Protein degradation
D. DNA replication
B
192
Which enzyme deficiency in the pentose phosphate pathway causes hemolytic anemia under oxidative stress?
A. Hexokinase
B. Glucose-6-phosphate dehydrogenase (G6PD)
C. Phosphofructokinase
D. Pyruvate kinase
B
193
The first law of thermodynamics states that:
A. Energy can be created or destroyed
B. Energy cannot be created or destroyed, only transformed
C. Entropy always decreases
D. Living systems generate energy from nothing
B
194
The second law of thermodynamics states that:
A. Energy is conserved
B. Entropy (tendency to disorder) always increases
C. All reactions are spontaneous
D. Heat cannot be converted to work
B
195
Free energy change (ΔG) determines:
A. Reaction rate
B. Reaction spontaneity
C. Enzyme amount
D. Substrate specificity
B
196
If ΔG < 0, the reaction is:
A. Endergonic (non-spontaneous)
B. Exergonic (spontaneous)
C. At equilibrium
D. Reversible only in enzymes
B
197
At equilibrium, ΔG equals:
A. Positive value
B. Negative value
C. Zero
D. One
C
198
ATP hydrolysis is a(n):
A. Endergonic reaction
B. Exergonic reaction
C. Reversible reaction only
D. Redox reaction
B
199
Coupled reactions occur when:
A. Two exergonic reactions combine
B. An endergonic reaction is driven by an exergonic one
C. Two irreversible reactions mix
D. No energy transfer occurs
B
200
Oxidation refers to:
A. Gain of electrons
B. Loss of electrons
C. Gain of hydrogen
D. Formation of ATP
B
201
Reduction refers to:
A. Loss of electrons
B. Gain of electrons
C. Loss of protons
D. Energy loss
B
202
Which coenzyme functions in oxidation-reduction reactions?
A. ATP
B. NAD⁺/NADH
C. CoA
D. TPP
B
203
In cells, oxidation is usually linked to:
A. Loss of hydrogen atoms
B. Gain of oxygen
C. Electron transfer to NAD⁺ or FAD
D. All of the above
D
204
Which of the following best defines homeostasis in metabolism?
A. Static state
B. Dynamic balance between anabolism and catabolism
C. Equilibrium state
D. Irreversible system
B
205
Which coenzyme functions in oxidation-reduction reactions?
A. ATP
B. NAD⁺/NADH
C. CoA
D. TPP
B
206
An increase in entropy (ΔS) makes a reaction:
A. More spontaneous
B. Less spontaneous
C. Unchanged
D. Inactive
A
207
Which pair acts as a biological redox couple?
A. ATP/ADP
B. NAD⁺/NADH
C. CoA/Acetyl-CoA
D. FAD/FADH₂
B and D
208
Which statement about energy metabolism is TRUE?
A. Catabolism requires ATP
B. Anabolism releases ATP
C. Catabolism produces ATP and reducing equivalents
D. Both consume energy
C
209
Which of the following statements about biomolecules is TRUE?
A. Carbohydrates store genetic information.
B. Lipids are amphipathic and form membranes.
C. Proteins are not polymers.
D. Nucleic acids are energy storage molecules.
B
210
Which of the following is not a component of a nucleotide?
A. Phosphate group
B. Sugar
C. Amino group
D. Nitrogenous base
C
211
Which of the following levels of protein structure is maintained primarily by peptide bonds?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
A
212
What is the main force stabilizing α-helices and β-sheets in proteins?
A. Disulfide bonds
B. Hydrogen bonds
C. Ionic bonds
D. Van der Waals interactions
B
213
Which amino acid can form disulfide bonds that stabilize tertiary structure?
A. Cysteine
B. Glycine
C. Serine
D. Methionine
A
214
Which amino acid has the smallest side chain and provides flexibility?
A. Glycine
B. Proline
C. Leucine
D. Valine
A
215
Which amino acid has a rigid, cyclic side chain that introduces kinks in polypeptides?
A. Proline
B. Tyrosine
C. Alanine
D. Histidine
A
216
Which of the following amino acids is aromatic and nonpolar?
A. Phenylalanine
B. Serine
C. Aspartic acid
D. Lysine
A
217
In sickle cell anemia, which amino acid substitution occurs?
A. Valine → Glutamic acid
B. Glutamic acid → Valine
C. Lysine → Arginine
D. Tyrosine → Cysteine
B
218
Which property explains why membranes self-assemble into bilayers?
A. Hydrophilic attraction
B. Hydrophobic effect
C. Ionic bonding
D. Hydrogen bonding
B
219
Which component of the plasma membrane acts as a fluidity buffer?
A. Cholesterol
B. Glycoprotein
C. Phosphatidylcholine
D. Triacylglycerol
A
220
Which type of transport moves molecules against a concentration gradient using ATP?
A. Simple diffusion
B. Facilitated diffusion
C. Active transport
D. Osmosis
C
221
The Na⁺/K⁺-ATPase pump moves:
A. 3 Na⁺ out, 2 K⁺ in
B. 2 Na⁺ in, 3 K⁺ out
C. Equal Na⁺ and K⁺ exchange
D. 1 Na⁺ and 1 K⁺ simultaneously
A
222
The GLUT-4 transporter is activated by:
A. Glucagon
B. Insulin
C. Epinephrine
D. Cortisol
B
223
Which sugar is a component of both RNA and DNA?
A. Fructose
B. Deoxyribose
C. Ribose
D. Glucose
C
224
The bond joining glucose and fructose in sucrose is a:
A. Glycosidic bond
B. Peptide bond
C. Hydrogen bond
D. Phosphodiester bond
A
225
Lactose intolerance results from deficiency of:
A. Amylase
B. Maltase
C. Lactase
D. Sucrase
C
226
Hurler and Hunter syndromes involve accumulation of:
A. Glycogen
B. Glycosaminoglycans (GAGs)
C. Proteins
D. Lipids
B
227
The enzyme inhibited by digoxin is:
A. Na⁺/K⁺-ATPase
B. Ca²⁺ ATPase
C. ATP synthase
D. Adenylate cyclase
A
228
Collagen requires which vitamin for proper cross-linking?
A. Vitamin C
B. Vitamin B₁₂
C. Vitamin D
D. Vitamin K
A
229
A patient with bleeding gums and fragile skin likely has:
A. Scurvy
B. Pellagra
C. Beriberi
D. Rickets
A
230
The fibrous protein that gives skin elasticity is:
A. Elastin
B. Keratin
C. Collagen
D. Myosin
A
231
Which of the following is a globular protein?
A. Collagen
B. Elastin
C. Hemoglobin
D. Keratin
C
232
The Bohr effect describes how:
A. pH and CO₂ affect O₂ binding by hemoglobin
B. Hemoglobin carries CO₂
C. Myoglobin releases oxygen
D. Temperature lowers O₂ affinity
A
233
A right shift in the oxygen dissociation curve means:
A. Increased O₂ affinity
B. Decreased O₂ affinity
C. No change in affinity
D. Irreversible binding
B
234
Which of the following is true of fetal hemoglobin (HbF)?
A. Lower O₂ affinity
B. Higher O₂ affinity than adult HbA
C. Same O₂ affinity
D. Does not bind O₂
B
235
A right shift in the oxygen dissociation curve means:
A. Increased O₂ affinity
B. Decreased O₂ affinity
C. No change in affinity
D. Irreversible binding
B
236
The primary storage form of lipids in adipose tissue is:
A. Cholesterol
B. Phospholipid
C. Triglyceride
D. Sphingomyelin
C
237
The lipid component responsible for myelin sheath insulation is:
A. Sphingolipid
B. Cholesterol
C. Phospholipid
D. Fatty acid
A
238
HDL functions to:
A. Deliver cholesterol to tissues
B. Transport cholesterol from tissues to liver
C. Synthesize bile acids directly
D. Convert fat to glucose
B
239
The process of breaking down triglycerides into fatty acids is called:
A. Lipolysis
B. Lipogenesis
C. β-oxidation
D. Transamination
A
240
Which vitamin acts as a cofactor for transaminase reactions?
A. Pyridoxal phosphate (Vitamin B₆)
B. Riboflavin
C. Thiamine
D. Niacin
A
241
Which of the following coenzymes carries acyl groups?
A. Coenzyme A (CoA)
B. NAD⁺
C. FAD
D. TPP
A
242
In competitive inhibition, which parameter changes?
A. Km increases
B. Vmax decreases
C. Km decreases
D. Both decrease
A
243
In noncompetitive inhibition:
A. Km increases, Vmax unchanged
B. Vmax decreases, Km unchanged
C. Both increase
D. Both decrease
B
244
The enzyme kinetics graph for allosteric enzymes is:
A. Hyperbolic
B. Sigmoidal
C. Linear
D. Parabolic
B
245
The main site of glycolysis is:
A. Cytoplasm
B. Mitochondria
C. Nucleus
D. Ribosome
A
246
Pyruvate dehydrogenase converts:
A. Pyruvate → Acetyl-CoA
B. Lactate → Pyruvate
C. Acetyl-CoA → Citrate
D. Citrate → Malate
A
247
The rate-limiting enzyme of glycolysis is:
A. Hexokinase
B. Phosphofructokinase-1 (PFK-1)
C. Pyruvate kinase
D. Glucose-6-phosphatase
B
248
The electron transport chain takes place in the:
A. Mitochondrial inner membrane
B. Cytosol
C. Outer membrane
D. Nucleus
A
249
Oxygen serves as:
A. Electron donor
B. Final electron acceptor
C. ATP source
D. Proton carrier
B
250
The total ATP yield from one molecule of glucose (aerobic) is approximately:
A. 2
B. 12
C. 30–32
D. 38–40
C
251
Which of the following is the common metabolic intermediate for carbohydrates, fats, and proteins?
A. Acetyl-CoA
B. Lactate
C. Glycerol
D. Pyruvate
A
252
The Krebs cycle directly produces:
A. NADH, FADH₂, and GTP
B. Only ATP
C. CO₂ only
D. NADPH only
A
253
β-oxidation of fatty acids occurs in the:
A. Cytosol
B. Mitochondrial matrix
C. Nucleus
D. Golgi apparatus
B
254
Ketone bodies are synthesized from:
A. Acetyl-CoA in liver mitochondria
B. Glucose in cytoplasm
C. Amino acids in nucleus
D. Glycerol in Golgi
A
255
During fasting, the brain mainly uses:
A. Fatty acids
B. Ketone bodies
C. Glucose from glycogen
D. Amino acids
B
256
The Cori cycle connects:
A. Liver and muscle
B. Brain and kidney
C. Heart and lung
D. Pancreas and intestine
A
257
In the Cori cycle, the liver converts:
A. Lactate → Glucose
B. Glucose → Lactate
C. Pyruvate → Alanine
D. Fatty acids → Ketones
A
258
In thermodynamics, a reaction with ΔG < 0 is:
A. Spontaneous (exergonic)
B. Nonspontaneous (endergonic)
C. At equilibrium
D. Impossible
A
259
The second law of thermodynamics states that:
A. Energy is constant and entropy increases
B. Energy can be created
C. ATP synthesis decreases entropy
D. Enzymes prevent energy loss
A
Biochemistry I
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